1. Field of the Invention
The present invention relates to a sheet metal member integrally having a peripheral wall surrounding a base plate, such as in piston components and a drive plate employed in the automatic transmission of an automobile, and a method of thickening a peripheral wall thereof. Specifically, the present invention relates to the employment of a thin disc-shaped sheet metal material, thereby forming a peripheral wall whose thickness is several times the thickness of the disc-shaped sheet metal material.
2. Description of the Prior Art
Conventionally, a technique for roll forming a sheet metal member integrated with a peripheral wall which is slightly thicker than a base plate, and surrounding the base plate by means of a forming roller, is often employed. However, it has been impossible to provide a method of thickening the peripheral wall of the sheet metal member so as to be several or more times the thickness of the base plate by employing the conventional roll forming method, and it has not been thought of to form the sheet metal member having a peripheral wall whose thickness reaches a value which is several times more than that of the base plate.
Therefore, in the sheet metal member integrally having a peripheral wall surrounding the base plate, such as in piston components, the sheet metal member having the peripheral wall whose thickness is increased several times the thickness of the base plate is conventionally formed by a cutting process. However, the yield on material in the cutting process is low, thereby causing an uneconomical state.
The present invention has been developed in view of the above mentioned circumstances. It is an object of the present invention to provide a sheet metal member integrally having a peripheral wall, surrounding the base plate, whose thickness is increased so as to be several times the thickness of the base plate.
It is another object of the present invention to provide a method of thickening a peripheral wall of the sheet metal member, enabling the thickness of the peripheral wall to be increased so that it is several times the thickness of the base plate.